This invention relates to controlling corrosion in a well which produces a hot and highly pressurized corrosive gas, by continuously injecting an oil-phase liquid containing a corrosion inhibitor. The invention applies to such a well which is in a relatively remote location and produces, or is near a well which produces, a gas containing a condensate inclusive of significant amounts of high-boiling, oil-soluble polar organic liquid components. The invention is particularly applicable to such a well in an offshore location.
Considerable information has been published in journal articles and patents regarding the problems of controlling corrosion in deep corrosive gas wells. For example, the article entitled "Deep Wells-A Corrosion Engineering Challenge" by R. N. Tuttle and T. W. Hamby (presented in a meeting in Toronto in April, 1975, and published in the October 1977 Materials Performance) points out that such wells may have bottomhole temperatures as high as 550.degree. F. and bottomhole pressures exceeding 22,000 psi. Also, in some such wells, the acid-gas content may represent more than half of the gas phase and the produced gas may be saturated with water and under saturated with respect to heavy hydrocarbons. In deep sour gas wells in the Thomasville-Piney Woods Field, such corrosion problems have been controlled by continuously circulating an oil containing a corrosion inhibitor within the well to maintain a corrosion-preventing oil-phase liquid film on the well conduits. A manufactured combination heavy oil/corrosion inhibitor mix was found to be effective at pressures of about 9,500 psi and 380.degree. F. As indicated in the article, such systems and their use have been made commercially available by a data generation program that is available to industry and governmental agencies. SPE paper No. 8310, "Corrosion Control-Deep Sour Gas Protection" by Morris C. Place, Jr. (presented September 1979) describes additional details of the corrosion-inhibiting procedure and lists numerous characteristics which are essential for a successful system. A paper entitled "Development of High Pressure Sour Gas Technology" by Tyler W. Hamby, Jr., Petroleum Technology, May 1981, discusses the graph from which the present FIG. 1 is taken, reviews the major problem areas, and discusses the progress made and problems remaining after about ten years since the high pressure sour gas field was discovered.
U.S. Pat. No. 4,295,979 is directed to the same type of corrosion inhibiting problem. It quotes a statement from the 1975 Tuttle and Hamby article on the need for an inhibitor-carrier oil "which would provide a high dew-point pressure at low concentration in the mixed gas-oil inhibitor phase" and says, "the present invention is such a system". The system described in the patent is a carrier oil which is manufactured by adding elemental sulphur to an amine activated dialkyldisulfide oil.